Here's what we know:
* Fountain pen: He was known to be a fan of fountain pens, and many sources mention him using one.
* Lined paper: He often used A4-sized lined paper, which was common in the UK where he lived and wrote.
* Notebooks: While not his primary tool, he also used notebooks to jot down ideas.
* Typewriter: Dahl did use a typewriter in later years for some editing and revisions, but he primarily wrote in longhand.
It's important to note that Dahl never publicly discussed his writing process in detail. These details about his writing tools come from anecdotes and biographical information.